:root {
  --ink: #17372e;
  --ink-soft: #315047;
  --muted: #60736b;
  --paper: #fffefb;
  --cream: #f3f5ef;
  --line: #d9e3da;
  --line-strong: #c7d6ca;
  --green: #2f7559;
  --green-dark: #1f5742;
  --green-deep: #153f31;
  --mint: #e9f3eb;
  --orange: #cf7b3c;
  --danger: #b85f5f;
  --danger-soft: #fff1ee;
  --review: #966d1f;
  --review-soft: #fff7df;
  --shadow-sm: 0 5px 16px rgba(24, 55, 44, .055);
  --shadow: 0 18px 46px rgba(24, 55, 44, .075), 0 2px 8px rgba(24, 55, 44, .035);
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC", sans-serif;
  --font-display: -apple-system, BlinkMacSystemFont, "SF Pro Display", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-reading: Charter, "Iowan Old Style", "Songti SC", "STSong", Georgia, serif;
  font-family: var(--font-sans);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: radial-gradient(circle at 8% -5%, rgba(214, 232, 216, .7), transparent 28rem), radial-gradient(circle at 100% 22%, rgba(246, 227, 208, .34), transparent 25rem), var(--cream); color: var(--ink); font-family: var(--font-sans); font-size: 16px; line-height: 1.6; -webkit-font-smoothing: antialiased; text-rendering: optimizeLegibility; }
::selection { background: #cfe4d4; color: var(--green-deep); }
button, input { font: inherit; }
button { cursor: pointer; border: 0; font-weight: 650; }
button:focus-visible, input:focus-visible, summary:focus-visible { outline: 3px solid rgba(47, 112, 87, .24); outline-offset: 2px; }
button:disabled { cursor: default; opacity: .45; transform: none !important; }
.shell { max-width: 1220px; margin: 0 auto; padding: 28px 30px 68px; }
.topbar { display: flex; align-items: center; justify-content: space-between; gap: 20px; margin-bottom: 36px; }
.brand { display: flex; align-items: center; gap: 12px; padding: 0; background: transparent; color: var(--ink); font-family: var(--font-display); font-weight: 780; letter-spacing: -.012em; text-align: left; }
.mark { display: grid; place-items: center; flex: 0 0 auto; width: 42px; height: 42px; border-radius: 14px; background: linear-gradient(145deg, #397e62, var(--green-dark)); color: white; font-weight: 820; box-shadow: 0 7px 18px rgba(34, 91, 68, .18); }
.brand small { display: block; margin-top: 1px; color: var(--muted); font-weight: 520; font-size: 11px; letter-spacing: .02em; }
.top-actions { display: flex; align-items: center; justify-content: flex-end; gap: 9px; }
.avatar { display: grid; place-items: center; width: 34px; height: 34px; border-radius: 50%; background: #d9e7dc; color: var(--green-dark); font-weight: 700; }
.muted { color: var(--muted); }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 44px; padding: 10px 17px; border-radius: 13px; font-weight: 700; letter-spacing: .01em; transition: transform .18s, background .18s, border-color .18s, box-shadow .18s; }
.btn-primary { background: linear-gradient(145deg, #397e62, var(--green)); color: white; box-shadow: 0 7px 17px rgba(47, 112, 87, .18); }
.btn-primary:hover { background: linear-gradient(145deg, var(--green), var(--green-dark)); transform: translateY(-1px); box-shadow: 0 10px 22px rgba(47, 112, 87, .22); }
.btn-secondary { background: rgba(255, 255, 255, .88); color: var(--green-dark); border: 1px solid var(--line); box-shadow: var(--shadow-sm); }
.btn-secondary:hover { border-color: #aec5b4; background: white; transform: translateY(-1px); }
.btn-ghost { background: transparent; color: var(--muted); }
.btn-ghost:hover { background: rgba(255, 255, 255, .65); color: var(--green-dark); }
.btn-wide { width: 100%; }
.compact-btn { min-height: 36px; padding: 8px 12px; }
.text-link { padding: 0; background: transparent; color: var(--green); font-weight: 700; }
.eyebrow { color: var(--orange); text-transform: uppercase; font-size: 11px; letter-spacing: .17em; font-weight: 820; }
.eyebrow.light { color: #d9edda; }
.hero h1 { margin: 10px 0 12px; font-family: var(--font-display); font-size: clamp(34px, 4vw, 48px); font-weight: 790; line-height: 1.14; letter-spacing: -.035em; }
.hero p { max-width: 790px; margin: 0; color: var(--muted); line-height: 1.78; font-size: 16.5px; }
.chapter-hero { position: relative; overflow: hidden; padding: 34px 36px; border: 1px solid rgba(203, 219, 206, .9); border-radius: 26px; background: linear-gradient(135deg, rgba(255, 254, 251, .96), rgba(235, 244, 236, .88)); box-shadow: var(--shadow); }
.chapter-hero::after { position: absolute; right: -38px; bottom: -74px; width: 210px; height: 210px; border: 34px solid rgba(47, 117, 89, .055); border-radius: 50%; content: ""; pointer-events: none; }
.back-home { margin: 0 0 18px -12px; }
.card { background: rgba(255, 254, 251, .96); border: 1px solid rgba(214, 225, 216, .94); border-radius: 22px; padding: 24px; box-shadow: var(--shadow); }
.section-title { display: flex; align-items: flex-end; justify-content: space-between; gap: 20px; margin: 34px 0 15px; }
.section-title h2 { margin: 0; font-family: var(--font-display); font-size: 21px; font-weight: 760; letter-spacing: -.018em; }
.section-title p { margin: 0; color: var(--muted); font-size: 13px; text-align: right; }
.progress { height: 8px; overflow: hidden; background: #e5ebe6; border-radius: 99px; }
.progress > i { display: block; height: 100%; border-radius: 99px; background: var(--green); transition: width .25s; }
.pill { display: inline-flex; align-items: center; gap: 6px; width: fit-content; padding: 6px 10px; border-radius: 99px; background: var(--mint); color: var(--green-dark); font-size: 12px; font-weight: 700; }
.pill.orange { background: #fff0df; color: #9a5c2e; }
.pill.locked { background: #ecefec; color: #87918c; }
.main-cta { position: relative; display: flex; align-items: center; justify-content: space-between; gap: 24px; overflow: hidden; margin: 28px 0 8px; padding: 30px 32px; border: 1px solid rgba(255, 255, 255, .1); border-radius: 26px; background: linear-gradient(135deg, #34785d 0%, #245d47 100%); color: white; box-shadow: 0 20px 45px rgba(29, 79, 59, .16); }
.main-cta::after { position: absolute; right: 16%; bottom: -92px; width: 220px; height: 220px; border: 38px solid rgba(255, 255, 255, .045); border-radius: 50%; content: ""; pointer-events: none; }
.main-cta > * { position: relative; z-index: 1; }
.main-cta h2 { margin: 6px 0 8px; font-family: var(--font-display); font-size: 26px; font-weight: 760; letter-spacing: -.02em; }
.main-cta p { margin: 0; color: #cde0d2; line-height: 1.6; }
.main-cta .btn { flex: 0 0 auto; min-width: 174px; background: white; color: var(--green-dark); }
.course-stage { margin-top: 26px; }
.course-stage + .course-stage { margin-top: 44px; padding-top: 4px; border-top: 1px solid rgba(220, 229, 221, .8); }
.course-stage > .section-title h2::before { display: inline-block; width: 6px; height: 18px; margin-right: 10px; border-radius: 99px; background: linear-gradient(var(--orange), #e9b17e); content: ""; vertical-align: -2px; }
.course-map { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 15px; }
.chapter-card { position: relative; display: flex; flex-direction: column; justify-content: space-between; width: 100%; min-height: 196px; overflow: hidden; color: var(--ink); text-align: left; transition: transform .18s, border-color .18s, box-shadow .18s; cursor: pointer; }
.chapter-card::before { position: absolute; inset: 0 auto 0 0; width: 4px; background: linear-gradient(180deg, var(--green), #94bda1); opacity: 0; content: ""; transition: opacity .18s; }
.chapter-card:hover, .chapter-card:focus-visible { transform: translateY(-4px); border-color: #b8cdbc; box-shadow: 0 20px 48px rgba(27, 59, 45, .12); }
.chapter-card:hover::before, .chapter-card:focus-visible::before { opacity: 1; }
.chapter-card.locked { cursor: default; opacity: .68; }
.chapter-card.locked:hover { transform: none; }
.chapter-number { display: block; margin-bottom: 15px; color: var(--green); font: 740 24px/1 var(--font-reading); letter-spacing: .03em; }
.chapter-card-title { display: block; margin: 0 0 8px; font-family: var(--font-display); font-size: 19px; font-weight: 750; letter-spacing: -.015em; }
.chapter-card-copy { display: block; margin: 0; color: var(--muted); line-height: 1.6; }
.card-foot { display: grid; grid-template-columns: 1fr auto; align-items: center; gap: 12px; margin-top: 22px; }
.chapter-path { margin: 22px 0 18px; padding: 26px; }
.chapter-path .section-title, .checkpoint-card .section-title { margin: 0 0 15px; }
.lesson-list { display: grid; gap: 10px; margin-top: 18px; }
.lesson-row { display: grid; grid-template-columns: 44px minmax(0, 1fr) auto auto; align-items: center; gap: 15px; padding: 16px 17px; border: 1px solid var(--line); border-radius: 16px; background: rgba(255, 255, 255, .82); box-shadow: 0 2px 7px rgba(24, 55, 44, .025); transition: border-color .18s, background .18s, transform .18s; }
.lesson-row:hover { border-color: var(--line-strong); background: white; transform: translateX(2px); }
.lesson-index { display: grid; place-items: center; width: 38px; height: 38px; border-radius: 12px; background: linear-gradient(145deg, #edf5ee, #e3eee5); color: var(--green-dark); font-weight: 820; box-shadow: inset 0 0 0 1px rgba(47, 117, 89, .035); }
.lesson-main h3 { margin: 0 0 5px; font-family: var(--font-display); font-size: 17.5px; font-weight: 730; letter-spacing: -.012em; }
.lesson-main p { margin: 0; color: var(--muted); line-height: 1.55; font-size: 13.5px; }
.checkpoint-card { padding: 26px; }
.source-note { color: var(--muted); line-height: 1.7; }
.study-wrap { max-width: 930px; margin: 0 auto; }
.study-head { display: flex; justify-content: space-between; align-items: center; gap: 16px; margin-bottom: 20px; color: var(--muted); font-size: 13px; }
.lesson-header { margin-bottom: 24px; }
.lesson-header h1 { margin: 9px 0 9px; font-family: var(--font-display); font-size: clamp(32px, 4vw, 45px); font-weight: 790; line-height: 1.15; letter-spacing: -.035em; }
.lesson-header p { margin: 0; color: var(--muted); font-size: 16.5px; line-height: 1.7; }
.step-tabs { display: flex; gap: 9px; margin: 0 0 20px; padding: 2px 2px 11px; overflow-x: auto; overscroll-behavior-inline: contain; scrollbar-width: thin; scrollbar-color: #aac3b1 transparent; }
.step-tabs::after { content: ""; flex: 0 0 6px; }
.step-tab { flex: 0 0 auto; max-width: 230px; padding: 10px 15px; border: 1px solid var(--line); border-radius: 99px; background: rgba(255, 255, 255, .82); color: var(--muted); font-size: 14px; font-weight: 620; white-space: nowrap; transition: background .18s, border-color .18s, color .18s; }
.step-tab:hover { border-color: var(--line-strong); color: var(--green-dark); }
.step-tab.active { border-color: #a8c9b0; background: linear-gradient(145deg, #edf6ee, #e4f0e7); color: var(--green-dark); font-weight: 750; box-shadow: 0 4px 12px rgba(33, 88, 65, .07); }
.step-content { min-height: 215px; padding: 31px 32px; }
.step-content h2 { margin: 0 0 19px; font-family: var(--font-display); font-size: 26px; font-weight: 760; letter-spacing: -.02em; }
.step-content p { margin: 0; color: var(--ink-soft); line-height: 1.9; font-size: 17.5px; }
.step-actions { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-top: 18px; }
.rule-list, .workflow-list { display: grid; gap: 12px; margin: 0; padding-left: 24px; color: #445b52; font-size: 16px; line-height: 1.7; }
.rule-list li::marker, .workflow-list li::marker { color: var(--green); font-weight: 800; }
.example-grid { display: grid; gap: 14px; }
.example-card { padding: 20px; border: 1px solid rgba(214, 228, 217, .7); border-radius: 16px; background: linear-gradient(145deg, #f5f9f4, #fbfcf9); }
.example-sentence { color: var(--green-dark); font: 650 20px/1.58 var(--font-reading); letter-spacing: .003em; }
.example-translation { margin: 6px 0 13px; color: var(--muted); }
.labels { display: flex; flex-wrap: wrap; gap: 7px; }
.label-chip { padding: 7px 10px; border-radius: 9px; background: white; color: #53675f; font-size: 12px; }
.notice { padding: 14px 16px; border-radius: 13px; background: #eef6ef; color: #416052; line-height: 1.7; }
.story-step { background: linear-gradient(135deg, #f2f8f2, #fbfcfa); }
.story-step h2 { margin-top: 16px; }
.build-step { overflow: hidden; }
.sentence-builder { display: flex; flex-wrap: wrap; gap: 10px; margin: 18px 0; }
.builder-piece { display: grid; gap: 5px; min-width: 145px; padding: 13px 15px; border: 1px solid #cfe2d2; border-radius: 14px; background: #eef7ef; }
.builder-piece strong { color: var(--green-dark); font: 650 17px/1.4 var(--font-reading); }
.builder-piece span { color: var(--muted); font-size: 12px; }
.builder-sentence { padding: 16px 18px; border-radius: 14px; background: linear-gradient(135deg, var(--green-deep), #244f3e); color: white !important; font: 650 19px/1.6 var(--font-reading) !important; letter-spacing: .01em; }
.compare-list, .mistake-list { display: grid; gap: 10px; }
.compare-row { display: grid; grid-template-columns: minmax(180px, .9fr) 1.1fr; gap: 14px; align-items: start; padding: 14px 15px; border-radius: 13px; background: #f4f8f3; }
.compare-row strong { color: var(--green-dark); font: 650 17px/1.5 var(--font-reading); }
.compare-row span { color: #53685f; line-height: 1.65; }
.compare-step .notice { margin-top: 14px; }
.mistake-row { display: grid; grid-template-columns: minmax(180px, .8fr) 1.2fr; gap: 14px; padding: 13px 15px; border: 1px solid #f2e1cc; border-radius: 13px; background: #fff8ef; }
.mistake-wrong { color: #9b5e37; font: 650 15.5px/1.6 var(--font-reading); }
.mistake-why { color: #53685f; line-height: 1.65; }
.quick-step summary { cursor: pointer; color: var(--green-dark); font-size: 20px; font-weight: 700; }
.quick-prompt { margin: 18px 0 !important; font-size: 17px !important; }
.quick-step .notice { margin-top: 12px; }
.practice-card { margin-top: 30px; padding: 31px 32px; border-top: 4px solid rgba(207, 123, 60, .75); scroll-margin-top: 18px; }
.practice-card h2 { margin: 7px 0 5px; font-family: var(--font-display); font-size: 28px; font-weight: 760; letter-spacing: -.02em; }
.practice-meta { margin: 0 0 24px; color: var(--muted); }
.question-prompt { margin: 19px 0; color: var(--ink); font-family: var(--font-display); font-size: 23px; font-weight: 680; line-height: 1.62; letter-spacing: -.008em; }
.choice-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 10px; margin-top: 14px; }
.choice-option { min-height: 54px; padding: 14px 16px; border: 1px solid var(--line); border-radius: 14px; background: rgba(255, 255, 255, .9); color: var(--ink); font-weight: 600; text-align: left; line-height: 1.5; transition: border-color .16s, background .16s, transform .16s; }
.choice-option:hover { border-color: #a9c5b0; background: #f6faf6; transform: translateY(-1px); }
.choice-option.selected { border-color: var(--green); background: var(--mint); color: var(--green-dark); box-shadow: 0 0 0 2px rgba(47, 112, 87, .08); }
.answer-input { width: 100%; min-height: 57px; margin-top: 12px; padding: 14px 17px; border: 1px solid var(--line); border-radius: 14px; background: white; color: var(--ink); font-size: 18px; box-shadow: inset 0 1px 2px rgba(24, 55, 44, .025); }
.answer-input:focus { border-color: var(--green); box-shadow: 0 0 0 3px rgba(47, 112, 87, .1); outline: 0; }
.answer-note { margin-top: 8px; padding: 10px 12px; border-radius: 12px; background: #fffaf0; color: #7f6a44; font-size: 14px; line-height: 1.6; }
.feedback { display: grid; gap: 11px; margin-top: 18px; padding: 18px; border: 1px solid var(--line); border-radius: 15px; line-height: 1.65; }
.feedback > strong { font-size: 18px; }
.feedback.good { border-color: #a8d0b1; background: #eef8ef; }
.feedback.bad { border-color: #e7b0a9; background: var(--danger-soft); }
.feedback.review { border-color: #e7cf8f; background: var(--review-soft); }
.answer { margin-top: 3px; }
.explanation { color: #445a51; line-height: 1.7; }
.topic { width: fit-content; padding: 6px 9px; border-radius: 9px; background: white; color: var(--green-dark); font-size: 12px; }
.done-card { padding: 50px 30px; text-align: center; }
.done-icon { font-size: 46px; }
.done-card h1 { margin: 12px 0 8px; }
.done-card p { max-width: 620px; margin: 0 auto; color: var(--muted); line-height: 1.7; }
.done-actions { display: flex; justify-content: center; gap: 10px; margin-top: 24px; flex-wrap: wrap; }
.chapter-practice { max-width: 930px; margin: 0 auto; }
.chapter-progress { position: sticky; top: 12px; z-index: 4; margin: 22px 0; padding: 17px 19px; border-color: rgba(194, 211, 199, .9); background: rgba(255, 254, 251, .93); box-shadow: 0 14px 34px rgba(27, 59, 45, .11); backdrop-filter: blur(12px); }
.chapter-progress-row { display: flex; justify-content: space-between; gap: 18px; margin-bottom: 10px; }
.chapter-progress-row span { color: var(--muted); font-size: 13px; }
.practice-group { margin: 28px 0 38px; }
.practice-group-title { display: flex; align-items: center; justify-content: space-between; gap: 16px; margin-bottom: 12px; padding: 0 4px; }
.practice-group-title h2 { margin: 0; font-family: var(--font-display); font-size: 22px; font-weight: 760; letter-spacing: -.02em; }
.practice-group-title span { color: var(--muted); font-size: 13px; }
.practice-question { display: grid; grid-template-columns: 42px minmax(0, 1fr); gap: 17px; margin-bottom: 13px; padding: 22px; border: 1px solid var(--line); border-radius: 18px; background: rgba(255, 254, 251, .96); box-shadow: 0 8px 24px rgba(27, 59, 45, .05); scroll-margin-top: 100px; }
.practice-question.unanswered { border-color: #dc8e85; box-shadow: 0 0 0 3px rgba(184, 95, 95, .08); }
.question-number { display: grid; place-items: center; align-self: start; width: 36px; height: 36px; border-radius: 12px; background: linear-gradient(145deg, #edf5ee, #e2eee5); color: var(--green-dark); font-weight: 820; }
.question-body { min-width: 0; }
.question-body h3 { margin: 3px 0 15px; color: var(--ink); font-family: var(--font-display); font-size: 19px; font-weight: 680; line-height: 1.66; letter-spacing: -.006em; }
.submit-checkpoint { min-height: 54px; margin-top: 8px; font-size: 17px; }
.question-result { margin-top: 10px; line-height: 1.65; }
.question-result.good { color: var(--green-dark); }
.question-result.bad { color: var(--danger); }
.question-result.review { color: var(--review); }
.question-result.neutral { color: var(--muted); }
.result-card { padding-top: 22px; }
.report-card { margin: 20px 0 30px; }
.report-card h1 { margin: 8px 0 18px; font-family: var(--font-display); letter-spacing: -.03em; }
.report-score { display: flex; align-items: center; gap: 22px; margin-bottom: 16px; }
.score-number { color: var(--green); font-size: 52px; font-weight: 850; line-height: 1; }
.score-label { color: var(--muted); line-height: 1.7; }
.summary-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 26px; margin-top: 24px; }
.summary-grid h3 { margin-top: 0; }
.summary-grid ul { padding-left: 20px; color: #486057; line-height: 1.8; }
.wrong-toolbar { display: flex; align-items: center; justify-content: space-between; gap: 14px; margin: 24px 0 14px; }
.search { width: min(390px, 100%); padding: 12px 14px; border: 1px solid var(--line); border-radius: 12px; background: white; }
.wrong-list { display: grid; gap: 12px; }
.wrong-item { display: grid; grid-template-columns: 1fr auto; gap: 20px; padding: 20px; border: 1px solid var(--line); border-radius: 17px; background: var(--paper); box-shadow: var(--shadow); }
.wrong-main { display: grid; gap: 8px; }
.wrong-main > strong { font-family: var(--font-display); font-size: 18px; line-height: 1.62; letter-spacing: -.006em; }
.wrong-main small { color: var(--muted); }
.wrong-main p { margin: 0; color: #4c6259; line-height: 1.7; }
.wrong-actions { display: flex; flex-direction: column; justify-content: center; gap: 8px; }
.empty { padding: 48px 20px; color: var(--muted); text-align: center; }
.auth-page { min-height: 100vh; display: grid; place-items: center; padding: 24px; background: radial-gradient(circle at 85% 15%, #e6f0e7, transparent 30%), var(--cream); }
.auth-box { width: min(450px, 100%); padding: 40px; border: 1px solid var(--line); border-radius: 28px; background: rgba(255, 254, 251, .96); box-shadow: 0 24px 60px rgba(24, 55, 44, .11); }
.auth-box .brand { margin-bottom: 34px; }
.auth-box h1 { margin: 8px 0; font-family: var(--font-display); font-size: 31px; font-weight: 780; letter-spacing: -.03em; }
.auth-box .lead { margin: 0 0 25px; color: var(--muted); line-height: 1.65; }
.field { display: grid; gap: 7px; margin-bottom: 16px; }
.field label { color: #486157; font-size: 13px; font-weight: 700; }
.field input { width: 100%; padding: 12px 13px; border: 1px solid var(--line); border-radius: 11px; background: white; }
.form-foot { margin-top: 18px; color: var(--muted); font-size: 13px; text-align: center; }
.alert { margin-bottom: 15px; padding: 11px 13px; border-radius: 11px; background: var(--danger-soft); color: var(--danger); font-size: 13px; }
.pending { max-width: 560px; margin: 9vh auto; }
.pending p { color: var(--muted); line-height: 1.7; }
.big-time { margin: 22px 0; font-size: 42px; font-weight: 800; letter-spacing: .04em; }
.table-wrap { overflow: auto; margin-top: 22px; }
.admin-table { width: 100%; border-collapse: collapse; font-size: 13px; }
.admin-table th, .admin-table td { padding: 14px 10px; border-bottom: 1px solid var(--line); text-align: left; white-space: nowrap; }
.admin-table th { color: var(--muted); font-weight: 650; }
.toast { position: fixed; right: 22px; bottom: 22px; z-index: 20; max-width: min(390px, calc(100vw - 32px)); padding: 12px 16px; border-radius: 12px; background: var(--ink); color: white; box-shadow: var(--shadow); }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
@media (max-width: 850px) {
  .shell { padding: 20px 18px 46px; }
  .course-map { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .lesson-row { grid-template-columns: 42px minmax(0, 1fr) auto; }
  .lesson-row > .pill { display: none; }
  .step-content { padding: 24px; }
  .choice-list { grid-template-columns: 1fr; }
  .compare-row, .mistake-row { grid-template-columns: 1fr; }
  .summary-grid { grid-template-columns: 1fr; }
}
@media (max-width: 600px) {
  .shell { padding: 16px 13px 38px; }
  .topbar { align-items: flex-start; margin-bottom: 26px; }
  .brand small, .username { display: none; }
  .top-actions { gap: 5px; }
  .top-actions .avatar { display: none; }
  .compact-btn { min-height: 34px; padding: 7px 9px; font-size: 12px; }
  .hero h1 { font-size: 31px; }
  .hero p { font-size: 15px; }
  .main-cta { align-items: stretch; flex-direction: column; padding: 23px; }
  .main-cta .btn { width: 100%; }
  .section-title { align-items: flex-start; flex-direction: column; gap: 5px; }
  .section-title p { text-align: left; }
  .course-map { grid-template-columns: 1fr; }
  .chapter-card { min-height: 164px; }
  .lesson-row { grid-template-columns: 36px minmax(0, 1fr); }
  .lesson-row .btn { grid-column: 1 / -1; width: 100%; }
  .study-head { align-items: flex-start; flex-direction: column; }
  .lesson-header h1 { font-size: 30px; }
  .step-tab { max-width: 195px; padding: 9px 12px; }
  .step-content, .practice-card { min-height: 0; padding: 21px 18px; }
  .step-content h2, .practice-card h2 { font-size: 23px; }
  .step-actions { align-items: stretch; flex-direction: column-reverse; }
  .step-actions .btn { width: 100%; }
  .builder-piece { flex: 1 1 42%; min-width: 0; }
  .builder-sentence { font-size: 16px !important; }
  .chapter-progress { top: 6px; }
  .chapter-progress-row { flex-direction: column; gap: 3px; }
  .practice-question { grid-template-columns: 32px minmax(0, 1fr); gap: 10px; padding: 16px 13px; }
  .question-number { width: 30px; height: 30px; }
  .question-body h3 { font-size: 16px; }
  .report-score { align-items: flex-start; flex-direction: column; }
  .score-number { font-size: 44px; }
  .wrong-toolbar { align-items: stretch; flex-direction: column; }
  .wrong-item { grid-template-columns: 1fr; }
  .wrong-actions { flex-direction: row; flex-wrap: wrap; justify-content: flex-start; }
  .auth-box { padding: 28px 21px; }
}